Pneumatic percussion tool



Feb. 1, 1966 R. L. SANDVIG 3,232,177

PNEUMATIC PERCUSSION TOOL Filed Aug. 10, 1964 4 Sheets-Sheet 1 /l d V vINVENTOR ROBERT L. SANDV/G BY MAHONEY,MILLER 8. RAMBO ATTORNEYS.

Feb. 1, 1966 R. L. SANDVIG 3,232,177

PNEUMATIC PERCUSSION TOOL Filed Aug. 10, 1964 4 Sheets-Sheet 2 IINVENTOR. 25 ROBERT L. SANDVIG E2 5 MAHONEY, MILLER & RAMBO ATTORNEYS.

- Feb. 1, 1966 INVENTQR. ROBERT L. SANDVIG BY MA I NEY. MILLER & RAMBOATTORNEYS.

Feb. 1, 1966 R. SANDVIG 3,232,177

ed Aug. 10, 1964 4 Sheets-Sheet 4.

NNNNN TOR. 5 5 ROBERT L. SANDVIG BY MAHONEY, MILLER & RAMBO ATTORNEYS.

United States Patent 3,232,177 PNEUMATKC PERCUSSiGN T001.

Robert L. Sandvig, Columbus, Ohio, assignor to The Jaeger MachineCompany, Qolumbus, Ohio, a corporation of Uhio Filed Aug. 10, 1964, Ser.No. 388,488 Claims. (Cl. 9131'7) This invention relates to a pneumaticpercussion tool. It has to do, more particularly, with the pneumaticpressure system and valve control system for obtaining and controllingthe reciprocation of a piston in the cylinder of a pneumatic tool.

With conventional pneumatic percussion tools, the automatic reversingvalve, which controls reciprocation of the piston in the cylinder, isshifted by pressure increases at the outer end of the piston or from thedirection of hammer movement in the cylinder. The reversing valveprovided according to the present invention is automatically shifted bypre-calculated pressure differentials. Furthermore, the ambient air isexhausted from the lower or outer end of the cylinder during thepercussion stroke of the piston. This unique arrangement results in thepiston striking a harder blow than is possible with prior art pneumaticpercussion tools.

In the accompanying drawings, the preferred embodiment of this inventionis shown and in these drawings:

FIGURE 1 is an axial sectional view of a pneumatic percussion toolembodying this invention.

FIGURE 2 is an enlarged axial sectional view through the cylinder of thetool at the location of the reversing valve and showing the valve in thepiston-down position.

FIGURE 3 is a similar view but showing the valve in the piston-upposition.

FIGURE 4 is a transverse sectional view taken along line 44 of FIGURE 2.

FIGURE 5 is a similar view but taken along line 5-5 of FIGURE 2.

FIGURE 6 is a detail of the valve in section taken substantially alongline 6-6 of FIGURE 4.

FIGURE 7 is an enlarged transverse sectional View taken along line 77 ofFIGURE 1.

FIGURE 8 is an enlarged transverse sectional view taken along line 8& ofFIGURE 1.

With reference to the drawings, the present invention is shown embodiedin a pneumatic tool of the demolition type but is not limited thereto.This tool is indicated as comprising generally a case or cylinder 16which has a piston hammer 11 reciprocably mounted therein to strike anaxially movable anvil block 12 that is adapted to engage the inner endof a workpiece or tool member 13 that is also slidably mounted in thecylinder at the outer end thereof which is the forward or lower endthereof. A novel valve arrangement for controlling this tool is providedaccording to this invention and is illustrated generally at 14 at theopposite or inner end of the cylinder which is the rear or upper endthereof.

The case or cylinder 1% may be made as an ordinary casting. Itpreferably comprises the main section 15 and an outer axially alignedguide or front head section 16 which are suitably connected. The section16 has a guide sleeve or front head bushing 17 removably mounted thereinfor receiving and guiding the tool 13, the sleeve 17 having a shoulder18 for cooperating with a similar shoulder on the section 16 to preventoutward displacement of the sleeve. Directly behind the sleeve 17 is ananvil lock seat guide or collar 19 in which the anvil block 12 isaxially movable. This member 19 is removably mounted in the rear orinner end of the cylinder section 16 and the forward or outer end of themain section 15 of the cylinder. The collar 19 has an inner tapered seat23 3,232,177 Patented Feb. 1, 1966 which cooperates with a similartapered shoulder on the anvil block 12 and is provided with an exteriorshoulder 24 which cooperates with a similar shoulder on the member 16.

The main section 15 of the cylinder has a cylindrical socket in which aseparate removable bushing or liner 25 of tubular form is disposed. Thisliner 25 can be slipped into the socket from the forward or inner openend of the cylinder section 15. The section 15 can be mounted on ahandle portion 2 0 of the tool casing by an attaching flange 26 at itsinner or rear end and cooperating bolts 27 or in any other suitablemanner. The removable liner 25 fits snugly into the socket in thecylinder section 15 and its outer or forward end abuts the rear end ofthe guide collar 19. The piston hammer 11 fits snugly in the liner 25for axial sliding movement.

As previously indicated, the cylinder section 15 may be a simple castingbeing of suitable tough cast metal since it need not be a hard andwear-resistant metal. The liner 25 is made of wear-resistant material,preferably hardened steel. Cast into the inner cylindrical socket wallof the section 15 are the necessary air-directing grooves or pets sages.In this instance, they are shown as being four grooves 39 (FIGURES 4-8)formed at angularly spaced positions and extending longitudinally in thesocket wall surface. Before the liner 25 is hardened, it is providedwith a pair of annular inwardly opening grooves or recesses 31 and 32 onits inner surface. These annular recesses are spaced axially apart adistance slightly less than the axial extent of the piston hammer 11 andthe recess 31 is spaced axially above the lower end of the cylinderchamber, as indicated in FIGURE 1. At the recess 31 (FIGURES l and 8),the liner is provided with a group of radial bores 33 corresponding innumber and angular position to the four grooves 23%. At the recess 32,the liner is provided with a group of radial bores 34, for example six,the bores being angularly spaced in a predetermined manner. These boresalso will be formed before the liner 25 is hardened. The respectivebores 33, as indicated, communicate with the grooves 39, as shown inFIGURE 7. To insure that the tubular liner 25 will be positioned in thecylindrical receiving socket so that the bores and grooves thereof willbe in angular align merit, a locating dowel pin 29 (FIGURES l5) isinserted at the inner or rear end of the cylinder section 15 andcooperates with radial aligned locating notches formed respectively inthe outer surface of the liner and the inner surface of the cylindersection at their adjacent ends. Thus, the liner 25 will be located in apredetermined fixed angular position within the cylinder section 15. Thesix bores 34 communicate with corresponding radial bores 35 (FIGURE 7)in the wall of the cylinder section 15. The aligning bores 34 and 35 andthe aligning bores and grooves 33 and 38, form part of the pneumaticsystem which actuates the piston hammer 11 and which is controlled bymeans including the reversing valve 14 previously mentioned.

Compressed air is supplied to the tool through a line 35 which isconnected to the cylinder section 15 at a swivel connection 37. Flow ofair into the cylinder is controlled by a throttle valve which comprisesa spring plunger 38 reciprocably mounted in the handle 29. This plunger38 is actuated by a trigger 39 which engages the outer end of theplunger 38, the plunger being normally held in its outer position by aspring 40. In this position, the valve plunger 38 closes a passageway 41leading from the line 36 to the valve 14. The trigger 39 is pivoted tothe handle 20 at 42 and is stopped in an outwardly swung position by thetransverse stop pin 43 which extends through an enlarged opening 44therein.

The handle 20 also has formed therein a reservoir or oil chamber 45 forlubricating oil which may be filled through a filler bore 46 normallyclosed by a removable plug (not shown). Oil under certain pressureconditions created by the valve 14 will seep from the chamber 45 througha porous plug 47 into a chamber 48 formed in the front face of thehandle 2&9. This plug may be made of porous bronze.

The reversing valve 14 is of novel construction and functions inaccordance with this invention to control the reciprocation of thepiston hammer 13. This valve 14- includes a tubular chest t) which isformed as a separate sleeve or bushing and is disposed at the rear orinner end of the cylinder section behind the liner in axially spacedrelationship thereto (FIGURES 1-3 and 6). The interior of the chest 5%communicates with the air passages or grooves in the cylinder section 15by means of four radial bores 51 (FIGURES 4 and 6) extending from anannular chamber 52 outwardly through the tubular wall of the chest 50and aligned with the grooves St? in the cylinder surface when the chestis properly positioned and set in the cylinder section 15. The dowel pin2% also locates the tubular chest so angularly within the cylindersection 15 cooperating with an aligning notch in the exterior of thechest as shown in FIGURES 2 and 3. It will be noted that the chamber 43is directly behind the valve cage 5t? and that the compressed air inletpassageway 41 communicates therewith. Another annular chamber 53 isprovided by a recess below the chamber 52 and is vented by a vent bore54 (FIGURE 5) extending radially outwardly through the valve chest 5thand the cylinder section 15.

The automatic valve member of the valve 14 is in the form of an annularpiston 55 (FIGURES 2 and 3) which is mounted for its axial movement onthe concentric stem of a valve guide as which includes a peripheralflange that is disposed between the adjacent ends of the chest 50 andthe liner 25, the flange being provided with a notch for receiving thedowel pin 29. The valve member 55 is provided with bores 58 extendingaxially therethrough and with. an annular groove 5h around itsperiphery. The flange 57 of the valve guide 56 is provided with bores 61extending axially therethrough. The upper or outer end of the chest 5%is flat and substantially closed but is provided with the inlet bores49.

A spring-pressed plunger 6% is axially mounted in the handle 20 inconcentric relationship with the stem of the guide 56 and engages theouter end thereof. The plunger is normally urged inwardly by acompression spring 63 which has its inner end disposed within the hollowplunger 6t and its outer end in engagement with the outer end of asocket 64 in the handle 20 in which the plunger is mounted for axialsliding movement. The spring-pressed plunger normally urges the guide 56into contact with the outer end of the liner 25.

In the operation of this. tool, compressed air for actuating the tool isadmitted by opening the normally closed valve 33. Assuming the piston 11is down, the valve 114 will be in the condition shown in FIGURE 2.Therefore, the admitted air will enter into the valve cage 59 throughthe bores 49 into the chamber 56a above the valve member 55 and thelower face of this member will be seated on the flange of the valveguide 56 seating at the lower valve face 55:: and thereby closing thevalve ports 58 and preventing flow of compressed air therethrough whichwould otherwise reach the cylinder chamber 110: above the piston 11,through the ports 61. The admitted compressed air does flow from thechamber 50a out through the bores 5i, through the valve cage wall, andinto the longitudinal grooves 3% (FIGURE 4) of the cylinder section 15and will emerge from those grooves through the bores 33 at the annularrecess 31 (FIGURE 1) of the cylinder liner 25, into the space 1112 belowthe piston 11. The build-up in volume of air below the piston 11 willthrust it upwardly at high velocity compressing the air in the chamberIla above the piston 11 and causing this compressed air to be forcedthrough the ports 61 into the chamber Bil b around the lower end of thevalve member 55'. The bores 58 of the valve member are closed at thistime. The face areas 55a, 55b, and 55c of the valve 55' are all equal.Therefore, when the air pressure in the lower chamber 5% exceeds the airpressure in the supply line 36 and the upper chamber 50a, the valvemember 55 shifts upwardly (FIGURE 3) seating at the upper valve face 55cto prevent compressed air from the line 36 from reaching the grooves Pt!through the radial valve cage bores 51, this occurring toward the end ofthe upstroke of the piston 11. As the piston 11 nears the extent of itsupstroke the exhaust bores 34 are exposed to exhaust the compressed airfrom the lower cylinder chamber lllb. The compressed air from the line.36 now flows through the chamber Stia and from it through the bores 53into the upper end of the chamber lia thrusting the piston hammer 11into its downstroke or percussion stroke. This downstrolre continuesuntil the upper end of the piston clears the exhaust groove 32(FIGURE 1) and exhaust bores 34 and the piston hammer It strikes theanvil 12;. and drives the tool 13 downwardly. The ambient air in frontof the hammer piston 11 in the forward or lower chamber 11b passesoutwardly through the radial bores 33, until these bores are covered bythe piston, into and through the grooves 3t? and from the upper ends ofthe grooves through the bores 51 into the annular groove 52 (FIGURE 3)and then into the communicating annular space 55 around the valve andfinally out to the amosphere through the vent bore 54 (FIGURE 5) whichcommunicates with the chamber 59. As indicated, in the downward strokeof the piston it will move below the bores 33 and compress air in thecylinder chamber below the piston which will serve as a pistoncushioning and returning force. Simultaneously, with the hammer piston11 striking the anvil I2, compressed air is exhausted from the chamberIla above the piston through the ports 3 and 35, exposed by downwardmovement of the piston, and due to the pressure drop in the lower valvechamber Stib through the ports 61, the pressure in the upper valvechamber 56a exceeds that in the lower valve chamber and causes the valvemember 5'5 to shift automatically again to the lower position shown inFIGURE 2 where it seats at the lower seal 55a thereby completing thepercussion cycle.

Lubricating oil is contained in the chamber 45 and at ambient pressureis contained by the porous plug 4-7 due to capillary action. When thevalve 33 is opened, however, compressed air enters into the chamber 48and from that chamber through the plug 4-7 pressurizing the chamber 45.However, when the valve 35 is again closed, the oil passes through theplug 47 into the chamber 48 until the pressure in the chambers 48 and 45is equalized. Thus, there will be a limited controlled flow oflubricating oil into the chamber 43 and the associated valve parts.

It will be apparent that with this valve arrangement the valve member 55is shifted by precalculated pressure differentials. Ambient air isexhausted from the lower or forward end of the cylinder during thepercussion stroke of the piston. This arrangement differs from prior arttools where the air ahead of the hammer piston is compressed and isrelied upon to shift the valve. With the arrangement of this invention,it is possible to obtain a greater precussive blow than with prior artarrangements.

The piston is moved axially in opposite directions under control of thereversing valve which also comprises the axially movable and axiallyaligned valve member. This member has the ports extending axiallytherethrough and the connections of the valve cage to the cylinder aresuch that the valve is moved axially in the same direction as the axialmovement of the piston. The valve member shifts downwardly as the piston11 moves downwardly (FIGURE 2) to bring about the upstroke of the pistonwhenever the upper chamber of the cylinder decompr'esses. It shiftsupwardly as the piston 11 moves upwardly (FIGURE 3) to bring about thedownstroke of the piston whenever the upper chamber of the cylinder ispressurized sutficiently by such upward movement of the piston. Duringthe downstroke or percussive stroke of the piston hammer, the air belowit is not compressed but is allowed to escape to the atmosphere.

As previously indicated, this valve arrangement is not limited to thetool described having the specific cylinder and piston arrangement. Forexample, the valve may be used in a structure where the piston and toolare rotated as disclosed in the copending application of Robert L.Sandvig, directed to Tool Retainer for a Pneumatic Hammer, Ser. No.388,487, filed August 10, 1964.

According to the provisions of the patent statutes, the principles ofthis invention have been explained and have been illustrated anddescribed in what is now considered to represent the best embodiment.However, it is to be understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallyillustrated and described.

Having tilfllS described this invention, what is claimed 1. A pneumaticpercussion tool comprising a cylinder; a piston hammer reciprocablymounted in the cylinder; selectively actuated means for supplyingcompressed air to the cylinder; means for automatically controlling thesupply of com-pressed air to the cylinder in accordance with actuationof said selectively actuated means, said last-named means comprising areversing valve; said cylinder having air passages which communicatetherewith at a point spaced from the forwardmost end of the cylinder andwhich commuicate with said reversing valve; said cylinder having ventpassages intermediate its length communicating with the atmosphere; saidvent passages and said air passages communicating with the cylinder atlocations spaced apart axially of the cylinder a distance slightly lessthan the axial extent of said piston; said reversing valve comprising atubular cage mounted in axial alignment with the cylinder at the rearend thereof and having a concentric valve guide positioned therewithin;a sleeve-like valve member mounted within said tubular cage and aroundsaid valve guide for axial movement; said valve cage having at its rearend inlet 'ports which lead into a first rear annular chamber formedtherein, said inlet .ports being connected to said selectively actuatedair-supplying means, said first chamber being provided with air-passageswhich communicate with said cylinder air-passages, said valve cage beingprovided with a second annular chamber intermediate its ends which isvented, said valve cage being provided with a third annular forwardchamber communicating by axial passages with the rear end of saidcylinder, said valve member being provided with passages leading axiallytherethrou-gh; said valve member when in its forward position with thepiston in its forward position having said third chamber connected tothe rear end of the cylinder, with said first chamber connected to saidinlet ports so as to permit fiow of air into said first chamber uponactuation of said selectively actuated means and then into said cylinderair passages to reach the space in said cylinder ahead of the pistonthrough said cylinder air passages, the space in said cylinder behindthe piston communicating with atmosphere through said cylinder ventpassages; air pressure supplied ahead of the piston by said selectivelyactuated means causing the piston to move rearwardly in the cylinder tothereby close the vent passages of the cylinder and to move the valvemember rearwardly to thereby connect the source of supply of compressedair through said valve inlet ports and said valve member ports throughsaid third chamber to said rear end of the cylinder, to interrupt flowfrom said inlet ports to said first chamber and the connected cylinderair passages and to connect the first chamber with the vented secondchamber to thereby vent said cylinder air passageways and the space inthe cylinder ahead of the piston to permit subsequent forward movementof the piston during actuation of said selectively actuated means, saidspace ahead of the piston venting continuously during the forward strokeof the piston until said cylinder air passages are closed as the pistonnears the extent of its forward movement.

2. A pneumatic percussion tool according to claim 1 including means forsupplying lubricating oil to the valve cage for lubricating movement ofsaid valve member therein, said means comprising a chamber for oilcommunicating with said valve cage through a porous plug which permitspassage of oil from said oil chamber to said cage.

3. A pneumatic percussion tool comprising a cylinder; a piston hammerreciprocably mounted in the cylinder; selectively actuated means forsupplying compressed air to the cylinder; means for automaticallycontrolling the supply of compressed air to the cylinder in accordancewith actuation of said selectively actuated means, said last-named meanscomprising a reversing valve; said cylinder having air passages whichcommunicate therewith at a point adjacent the forwardmost end of thecylinder and which communicate with said reversing valve; said cylinderhaving vent passages intermediate its length communicating with theatmosphere; said vent passages and said air passages communicating withthe cylinder at 10- cations spaced apart axially of the cylinder; saidreversing valve comprising a tubular cage mounted in axial alignmentwith the cylinder at the rear end thereof; a concentric sleeve-likevalve member mounted within said tubular cage for axial movement; saidvalve cage having at its rear end inlet ports which lead into a firstrear annular chamber formed therein, said inlet ports being connected tosaid selectively actuated air-supplying means, said first chamber beingprovided with air-passages which communicate with said cylinderair-passages, said valve cage being provided with a second annularchamber intermediate its ends, which is vented, said valve cage beingprovided with a third annular forward chamber communicating iby passageswith the rear end of said cylinder, said valve member being providedwith passages leading therethrough; said valve member when in itsforward position with the piston in its forward position having saidthird chamber connected to the rear end of the cylinder, with said firstchamber connected to said inlet ports so as to permit flow of air intosaid first chamber upon actuation of said selectively actuated means andthen into said cylinder air passages to reach the space in said cylinderahead of the piston through said cylinder air passages, the space insaid cylinder behind the piston communicating with atmosphere throughsaid cylinder vent passages; air pressure supplied ahead of the pistonby said selectively actuated means causing the piston to move rearwardlyin the cylinder to thereby close the vent passages of the cylinder andto move the valve member rearwardly to thereby connect the source ofsupply of compressed air through said valve inlet ports and said valvemember ports through said third chamber to said rear end of thecylinder, to interrupt flow from said inlet ports to said first chamberand the connected cylinder air passages and to connect the first chamberwith the vented second chamber to thereby vent said cylinder airpassageways and the space in the cylinder ahead of the piston to permitsubsequent forward movement of the piston during actuation of saidselectively actuated means, said space ahead of the piston ventingcontinuously during the forward stroke of the piston until said cylinderair passages are closed as the piston nears the extent of its forwardmovement.

4. A pneumatic tool com-prising a cylinder; a piston reciprocablymounted in the cylinder; selectively actuated means for supplyingcompressed air to the cylinder; means for automatically controlling thesupply of compressed air to the cylinder in accordance with actuation ofsaid selectively actuated means, said last-named means comprising areversing valve; said cylinder having air passages which communicatetherewith at a forward point along the cylinder and which communicatewith said reversing valve; said cylinder having vent passages axiallybehind said cylinder air passages communicating with the atmosphere;said reversing valve comprising a valve member mounted within said cagefor reciprocal movement; said valve cage having inlet ports which leadinto a first chamber formed therein, said inlet ports being connected tosaid selectively actuated airsu-pplying means, said first chamber beingprovided with air-passages which communicate with said cylinderairpas'sages, said valve cage being provided with a second chamber whichis vented, said valve cage being provided with a third chambercommunicating by passages with the rear end of said cylinder, said valvemember being provided with passages leading thereth-rough; said valvemember when in one position with the piston in its forward positionhaving said third chamber connected to the rear end of the cylinder,with said first chamber connected to said inlet ports so as to permitflow of air into said first chamber upon actuation of said selectivelyactuated means and then into said cylinder air passages to reach thespace in said cylinder ahead of the piston through said cylinder airpassages, the space in said cylinder behind the piston communicatingwith atmosphere through said cylinder vent passages; air pressuresupplied ahead of the piston by said selectively actuated means causingthe piston to move rearwardly in the cylinder to thereby close the ventpassages of the cylinder and to move the valve member to thereby connectthe source of supply of compressed air through said valve inlet portsand said valve member ports through said third chamber to said rear endof the cylinder, to interrupt flow from said inlet ports to said firstchamber and the connected cylinder air passages and to connect the firstchamber with the vented second chamber to thereby vent said cylinder airpassageways and the space in the cylinder ahead of the piston to permitsubsequent forward movement of the piston during actuation of saidselectively actuated means, said space ahead of the piston ventingcontinuously during the forward stroke of the piston (until saidcylinder air passages are closed as the piston nears the extent of itsforward movement.

5. A pneumatic tool comprising a cylinder; a piston reciprocably mountedin the cylinder; a source of supply of compressed air for the cylinder,means for automatically controlling the supply of compressed air to thecylinder from said source and including a reversing valve; said cylinderhaving air passages which communicate therewith and with said reversingvalve; said cylinder having vent passages axially spaced from saidcylinder air passages communicating with the atmosphere; said reversingvalve comprising a cage; a valve member mounted within said cage forreciprocal movement; said valve cage having inlet ports which lead intoa first chamber formed therein, said first chamber being provided withair-passages which communicate with said cylinder air-passages, saidvalve cage being provided with a second chamber which is vented, saidvalve cage being provided with a third chamber communicating by passageswith the rear end of said cylinder, said valve memher being providedwith passages leading therethrough; said valve member when in oneposition with the piston in its forward position having said thirdchamber connected to the rear end of the cylinder, with said firstchamber connected to said inlet ports so as to permit flow of air intosaid first chamber from said compressed air source and then into saidcylinder air passages to reach the space in said cylinder ahead of thepiston through said cylinder air passages, the space in said cylinderbehind the piston communicating with atmosphere through said cylindervent passages; air pressure supplied ahead of the piston causing thepiston to move rearwardly in the cylinder to thereby close the ventpassages of the cylinder and to move the valve member to thereby connectthe source of supply of compressed air through said valve inlet portsand said valve member ports through said third chamber to said rear endof the cylinder, to interrupt flow from said inlet ports to said firstchamber and the connected cylinder air passages and to connect the firstchamber with the vented second chamber to thereby vent said cylinder airpassageways and the space in the cylinder ahead of the piston to permitsubsequent forward movement of the piston during supply of compressedair from said source, said space ahead of the piston ventingcontinuously during the forward stroke of the piston until said cylinderair passages are closed as the piston nears the extent of its forwardmovement.

References Cited by the Examiner UNITED STATES PATENTS 2,164,970 7/1939Van Sittert et a1. 91-556 2,254,695 9/ 1941 Fuehrer 91-239 2,613,64610/1952 Gillerstnum 91-3l7 3,038,447 6/1962 OFlarrell 9l-317 SAMUELLEVINE, Primary Examiner.

P. E. MASLOUSKY, Assistant Examiner.

1. A PNEUMATIC PERCUSSION TOOL COMPRISING A CYLINDER;